This invention relates to water distribution for irrigation purposes and, more particularly, to a water distribution plate for a rotatable sprinkler head.
Sprinkler heads of the type disclosed in U.S. Pat. No. 4,660,766 include a sprinkler body or housing having an inlet which is adapted to be connected to a source of water under pressure. The outlet is defined by a nozzle that directs the water under pressure communicating with the sprinkler body as a primary stream into the atmosphere along a generally vertically extending axis. A rotary water distribution plate (also referred to as a xe2x80x9crotor platexe2x80x9d) is provided for receiving the primary stream and directing it outwardly in a circular distribution pattern. A viscous damper mechanism is provided for reducing the rotational speed of the distribution plate from a relatively high whirling speed that would occur without the viscous damper, to a relatively slow speed.
One advantage of this type of sprinkler is that by limiting the rotational speed of the rotor plate, the water contacting the rotor plate can be projected outwardly so that stream integrity is maintained beyond the plate. Thus, the water distribution pattern can be made to closely simulate the highly desirable water distribution pattern of an impact sprinkler head.
Rotor plates are known that simply redirect the vertical stream to a substantially horizontal stream, or that first divide the primary stream into two or more streams through the use of grooves or channels radiating from the center of the rotor plate.
Rotation of the rotor plate is achieved by curving the one or more water distribution grooves or channels toward the exit ends of the grooves or channels, or by offsetting the grooves or channels from the center of rotation of the plate. Thus, water exiting the grooves causes the plate to rotate in a well understood manner. An example of a multi-channel rotor plate configuration is shown in commonly owned U.S. Pat. No. 4,796,811.
A disadvantage of the prior designs is that the radial distribution pattern has a smaller throw radius than if the grooves were straight and on center. Another disadvantage is the difficulty in maintaining a generally consistent rotation speed over a flowrate and pressure range. It is also a continuing objective to achieve good uniformity of the wetted area for all nozzle sizes, and at the same time, to increase the radius of throw so that the number of sprinklers required for a given area can be reduced.
In one exemplary embodiment of the present invention, a water distribution plate, or rotor plate, includes a surface incorporating individual pairs of channels that are shaped to perform different functions. A first pair of channels (referred to as xe2x80x9cdrive channelsxe2x80x9d) causes the plate to rotate when impinged by a stream emitted from a nozzle. A second pair of channels (referred to as xe2x80x9cbrake channelsxe2x80x9d) tends to slow rotation of the plate, while a third set of channels (referred to as xe2x80x9crange channelsxe2x80x9d) is substantially neutral with respect to plate rotation but increases the range or throw radius of the stream. Two additional but larger channels (referred to as xe2x80x9cfill channelsxe2x80x9d) serve primarily to fill in the pattern between the sprinkler and the maximum stream throw radius. By separating the functions of drive, range, and braking in various channels, it is possible to enhance desirable performance parameters including radius of throw, distribution pattern, and consistency of rotation speeds.
The plate itself is a disk-like member, one end of which is provided with a blind bore or the like to facilitate attachment of the plate to, for example, the damping device of a viscous damped sprinkler. The opposite end is formed with the above mentioned channels, with each channel extending generally from the center of the plate, radially outwardly to an exit location along the side wall of the plate. It will be appreciated that the grooves or channels transition from a sharply angled orientation (i.e., at an acute angle relative to the axis of the rotation that is substantially coincident with the stream emitted from the nozzle) at the plate center to a generally horizontal orientation at the plate periphery to thereby radially distribute the stream.
In one embodiment, a first group of drive, range and brake channels are located substantially diametrically opposite a second group or set of similar (mirror image) channels, with a pair of fill channels separating the two groups. The drive channels each comprise a substantially flat bottomed channel with steeply sloped sides. The drive channels curve from entrance to exit, so that the water exit is offset from the radial center, thus causing the disk to rotate in a direction opposite the direction of curvature as water flows through the channels. Note that the two drive channels on opposite sides are curved in opposite directions so that the offsets of both contribute to the drive function.
The range channels lie between adjacent drive and brake channels, and are also generally diametrically opposite each other. Each range channel has a substantially V-shaped cross-section at its radially innermost or entrance point, quickly transitioning to a substantially U-shaped cross-section for substantially its entire length, with upwardly curved side walls tapering outwardly from the center for only a short radial distance, and then exhibiting a substantially constant width to the exit location in the peripheral wall. These channels provide tight streams with maximum radius of throw and good wind fighting capability.
The brake channels are also generally diametrically opposed to each other, and are generally similar in cross-section to the drive channels, but they are oppositely curved and the flat bottom has a slightly greater width. In addition, the radially inner portions of the brake channels are smaller in cross-section than the radially inner portions of the drive channels. This means that the drive channels carry larger volumes of the stream at smaller nozzle sizes. For larger nozzles, the drive and brake channels have comparable flows. This arrangement helps counteract the tendency of the plates to rotate faster with larger nozzles.
In the preferred arrangement, these two groups of special function channels are substantially diametrically opposed, and as briefly noted above, are separated from each other in both directions by a fill channel, each fill channel occupying a space on the disk approximately equal to one of the two groups of three channels described above. Depending on nozzle size, the fill channels may or may not exhibit drive or brake forces, but these channels are designed primarily to ensure that the sprinkling pattern is filled in between the sprinkler and the maximum radius of throw.
In another embodiment, an alternating arrangement of relatively thin range and drive channels extend about the entire plate, with water exit angles of the range channels being less than the water exit angles of the drive channels. In this embodiment, there are twelve of each type of channel, all of which are slightly offset from the plate center. The shape of the plate is different from the first described embodiment in that the center of the plate is generally conical, such that the channels have a greater vertical direction component, transitioning to horizontal closer to the outermost tip of the plate. This example does not require brake channels for acceptably consistent rotation speeds.
Accordingly, in one aspect, the invention relates to a rotor plate for a sprinkler comprising a water impingement surface bounded by an annular peripheral wall and having a radial center, and adapted to be impinged upon by a stream emitted from a nozzle, the water impingement surface formed to include at least one radially extending drive channel having an entrance proximate the radial center and an exit in the peripheral wall, at least one drive channel curving from entrance to exit in a first direction so as to cause the plate to rotate when the stream exits the plate at an offset from the center of rotation; at least one range channel extending substantially radially with little or no curving, from entrance to exit; and at least one brake channel curving from entrance to exit in a second direction opposite the first direction to thereby resist rotation of the plate caused by at least one drive channel.
In another aspect, the invention relates to a rotor plate adapted to be supported on a shaft in axial alignment with a nozzle in a sprinkler head, the rotator plate comprising an annular member having water distribution channels formed on a surface thereof, the channels formed and arranged to radially distribute a stream emitted from the nozzle, alternating ones of the channels curved along their radial lengths to establish first water exit angles and corresponding offsets relative to a radial center line, such that water flowing through the alternating channels will cause the plate to rotate; remaining channels between the alternating channels curved along their radial lengths to establish second water exit angles and corresponding offsets less than the first water exit angles.
In still another aspect, the invention relates to a rotor plate for a sprinkler comprising an annular member having a water distribution surface formed with a plurality of substantially radial channels, formed with a first plurality of the channels having curvatures along their respective radial lengths establishing first water exit angles at exit ends of the channels, and a second plurality of the channels having curvatures along their respective radial lengths establishing second water exit angles at exit ends of the second plurality of channels, the second water exit angles less than the first water exit angles.